Women's diabetes risk increases after breast cancer

Women with a breast cancer history are at an increased risk of developing type 2 diabetes compared to their peers who've never had breast cancer, a new study showed. Women who undergo chemotherapy for treatment of their breast cancer also have a greater chance of becoming diabetic. However, the risk over time differs between these two groups.

"There is no reason for breast-cancer survivors to be alarmed," Dr. Lorraine Lipscombe, a research scientist at Women's College Research Institute in Toronto and the study's lead researcher, told The Globe and Mail. "Rather, this is something that physicians -- and women themselves -- should be aware of so they can get appropriate treatment during follow-up cancer care."

Two years after being diagnosed with breast cancer, women's chances of developing diabetes increased by 7 percent, but that risk increased to 21 percent after 10 years, according to the study results reported by Nurse.com. The study was published in the December issue of Diabetologia, the journal of the European Association for the Study of Diabetes.

In women who received chemotherapy, the risk was more than three times greater (24 percent) in the initial two-year window, but after 10 years, it dropped to 8 percent.

For the study, which spanned a period from 1996 to 2008, Lipscombe and colleagues examined the medical records of 24,976 breast cancer survivors and an additional 124,880 women with no breast cancer history -- all post-menopausal and over age 55. About 1 in 10 of the women included in the study became diabetic.

A possible explanation for the results of the chemotherapy group is the use of steroids for nausea often given with this cancer treatment, The Globe and Mail indicated. Steroids can elevate blood sugar, cause weight gain and alter insulin production, setting the stage for diabetes. The drop-off in risk over time could be due to the eventual dissipation of the steroid side effects or the women no longer being followed after two years' time, Nurse.com explained.

It's unclear why the risk of diabetes increased for breast cancer survivors who didn't get chemotherapy. Yet, diabetes and breast cancer have been shown to be linked. For instance, women with diabetes have greater chances, about a 20 percent higher rate, of developing breast cancer than those without diabetes. Diabetic women also are 50 percent more likely to die from breast cancer.

The connection between the two diseases suggests certain risk factors are common to both, insulin resistance, for example. Similarly, both share preventative measures, namely a healthy diet and exercise.

Researchers said further work is warranted to determine which post-breast cancer women have a greater risk of developing diabetes, CBC News noted.

"In the meantime, greater diabetes screening and prevention strategies among breast cancer survivors may be warranted," the study authors added.